In a semiconductor storage device such as an iPCM (interfacial Phase-Change Memory), a memory layer of a storage element is formed on a lower electrode in some cases. In these cases, if the crystal state and the flatness (morphology) of a surface of the lower electrode are poor, the crystallinity (crystal structure) of the memory layer on the lower electrode is deteriorated.
For example, a memory layer of the iPCM is formed by stacking a plurality of recording layers on a lower electrode. Because the lowermost recording layer deposited first on the lower electrode functions as a seed layer for other recording layers, the crystallinity of the lowermost recording layer influences the crystallinities of the other recording layers. Therefore, the crystallinity of the lowermost recording layer is an important factor to define the property of the memory. The crystallinity of the lowermost recording layer depends on the crystal state and the flatness of a surface of the lower electrode located thereunder. That is, when the crystal state and the flatness of the surface of the lower electrode are poor, the crystallinity of the lowermost recording layer also becomes poor. Therefore, to obtain a memory with a good property, a lower electrode having a favorable crystal state and being flat is demanded.